Table 2. Newcastle-Ottawa scale quality assessment results.

First author	Year	Reference	Selection	Comparability	Outcome	Total
Liu	2012	[4]	★★★	★★	★★	7
Wang	2013	[5]	★★★	★★	★★	7
Abue	2015	[6]	★★★	★★	★★	7
Goto	2018	[7]	★★★	★★	★★	7
Kawamura	2019	[8]	★★★	★★	★★★	8
Mikamori	2017	[14]	★★★	★★	★★★	8
Kong	2010	[16]	★★★	★★	★★	7
Yu	2017	[17]	★★★	★★	★★	7
Takahasi	2018	[23]	★★★	★★	★★	7
Li	2013	[24]	★★★	★★	★★★	8
Tavano	2013	[26]	★★★	★★	★★	7
Liao	2018	[27]	★★★	★★	★★	7
Schultz	2012	[28]	★★★	★★	★★	7
Wang	2019	[33]	★★	★	★★★	6
Nakata	2011	[35]	★★	★	★★★	6
Preis	2011	[36]	★★★	★★	★★	7
Nguyen	2016	[37]	★★★	★★	★★	7
Yang	2017	[38]	★★★	★★	★★★	8
Yu	2010	[39]	★★★	★★	★★★	8
Gu	2016	[40]	★★★	★★	★★	7
Zhu	2018	[41]	★★	★	★★	5
Dillhoff	2008	[43]	★★	★	★★★	6
Giovannetti	2010	[44]	★★★	★★	★★★	8
Hwang	2010	[45]	★★★	★★	★★★	8
Jamieson	2011	[46]	★★★	★★	★★	7
Nagao	2012	[47]	★★★	★★	★★	7
Caponi	2013	[48]	★★★	★★	★★★	8
Kadera	2013	[49]	★★★	★★	★★★	8
Ma	2013	[50]	★★★	★★	★★	7
Papaconstantinou	2013	[51]	★★★	★★	★★★	8
Donahue	2014	[52]	★★★	★★	★★★	8
Frampton	2014	[53]	★★★	★★	★★	7
Mitsuhashi	2015	[54]	★★★	★★	★★	7
Vychytilova-Faltejskova	2015	[55]	★★	★	★★	5
Morinaga	2016	[56]	★★★	★★	★★★	8
Benesova	2018	[57]	★★★	★★	★★	7
Xi	2018	[58]	★★	★	★★★	6
Zhang	2018	[59]	★★	★	★★★	6
Zhao	2018	[60]	★★★	★★	★★★	8
Diao	2018	[61]	★★	★	★★	5
Wu	2018	[62]	★★★	★★	★★	7
Liang	2018	[68]	★★	★	★★★	6
Jiang	2015	[69]	★★	★	★★	5
Zou	2015	[70]	★★★	★★	★★	7
Yu	2018	[82]	★★★	★★	★★★	8
Yu	2010	[109]	★★★	★★	★★★	8
Paik	2015	[110]	★★★	★★	★★★	8
Liu	2016	[111]	★★★	★★	★★★	8
Ikenaga	2010	[112]	★★★	★★	★★★	8
Shao	2017	[113]	★★	★	★★★	6
Shi	2018	[114]	★★	★	★★★	6
Li	2013	[121]	★★★	★★	★★	7
Zhu	2014	[122]	★★★	★★	★★	7
Li	2015	[123]	★★★	★★	★★★	8
Sarkar	2013	[125]	★★	★	★★★	6
Wang	2016	[126]	★★★	★★	★★	7
Lee	2013	[127]	★★★	★★	★★	7